Mortgage Recast Calculator

Compare recasting a mortgage after a lump sum against keeping the existing payment: cash flow freed versus interest saved.

Last reviewed 2026-08-01

Free · No sign-up · Runs in your browser

A recast is the quiet alternative to a refinance. You pay a lump sum against the balance and the servicer recalculates the payment over the same remaining term at the same rate. There is no underwriting, no appraisal, no new note and typically a small administrative fee rather than thousands in closing costs.

What a recast gives you is lower required monthly cash flow. What it costs is interest, because stretching a smaller balance across the original term keeps you in the loan for the full remaining years. The alternative - paying the lump sum and continuing to pay the old amount - saves considerably more and clears the loan sooner. This calculator prices both so the trade is explicit.

Result

Payment after recast

$1,730

Current payment: $2,100
Monthly reduction: $371
Annual cash flow freed: $4,448
Interest saved by recasting: $60,092
Interest saved by keeping the payment: $164,232
Extra interest a recast costs: $104,141
Months saved by keeping the payment: 106 months
Recast fee: $300

A recast keeps the rate and the remaining term and recalculates the payment on the smaller balance. It is not a refinance and there is no underwriting, which is why the fee is small.

Paying the lump sum and keeping the old payment saves more interest and clears the loan sooner. Recasting buys lower required monthly cash flow instead - a genuine benefit if the budget is tight, but it costs interest.

Not every loan or servicer permits recasting, and most set a minimum lump sum. Ask before sending the money.

How to use the mortgage recast calculator

Enter the current balance, rate and years remaining.
Enter the lump sum and the recast fee your servicer charges.
Compare the recalculated payment against the current one.
Compare the interest saved by recasting against the interest saved by keeping the old payment.

What people use this for

Reducing a mortgage payment after selling a previous property.
Lowering required monthly outgoings without refinancing at a higher current rate.
Deciding between recasting and simply overpaying.
Keeping a low legacy rate while reducing the payment.

Worked examples

Every figure below is produced by running this calculator against the example inputs, so the numbers always match the tool.

A recast after a property sale

$340,000 balance at 5.9% with 27 years left, $60,000 lump sum, $300 fee.

Payment after recast: $1,730
Monthly reduction: $371
Extra interest a recast costs: $104,141

A smaller recast for cash flow

$250,000 balance at 6.4% with 24 years left, $25,000 lump sum, $250 fee.

Payment after recast: $1,531
Annual cash flow freed: $2,041
Interest saved by keeping the payment: $73,961

Recast versus refinance

A refinance replaces the loan, which means new underwriting, new closing costs and - critically - the rate available today. A borrower holding a rate well below the current market has a strong reason to avoid that.

A recast keeps the note, the rate and the remaining term. The only thing that changes is the payment. For anyone sitting on an attractive rate who wants lower monthly outgoings, it is usually the better instrument, and it costs a fraction of a refinance.

The interest cost of recasting

Because the recalculated payment is spread over the full remaining term, a recast keeps you in the loan to the original end date. Paying the same lump sum and holding the old payment ends the loan years earlier and saves substantially more interest.

The difference between those two totals is what a recast costs, and it is worth knowing before choosing. Lower cash flow is a real benefit and it is not free.

Not every servicer offers it

Recasting is a servicer policy rather than a right. Most conventional loans permit it; many government-backed programmes do not. Servicers usually set a minimum lump sum and a fee, and both vary.

Ask before making the lump sum payment, because a payment sent without a recast request is simply an overpayment - beneficial, but with no change to the required monthly payment.

Methodology and assumptions

What this calculator does, and what it deliberately does not do.

The recast payment is the standard amortised payment on the reduced balance over the same remaining term at the same rate.
The keep-payment comparison applies the original payment to the reduced balance, which shortens the schedule.
Interest totals are compared across all three cases: no change, recast, and keeping the payment.
The fee is reported separately rather than folded into the interest figures.
Results are estimates. Real quotes depend on credit, income, property, loan programme and lender pricing at the time of application.
Nothing you type is transmitted or stored - the calculation runs entirely inside your browser.

This calculator is provided for informational and educational purposes only. Results are estimates and may not reflect actual rates, fees, taxes, or market conditions.

This website is not a lender, a mortgage broker or a financial adviser. It does not originate loans, does not accept applications and does not forward your details to anyone.

Actual loan terms depend on credit history, income, the property, the loan programme and lender pricing at the time of application. Only a lender can tell you what you qualify for.

Frequently asked questions

Does a recast change my interest rate?

No. The rate, the note and the remaining term all stay the same. Only the payment is recalculated.

Is there underwriting?

Generally not. There is no new loan, so no credit check, income verification or appraisal is normally required.

What does it cost?

A modest administrative fee in most cases, far below refinance closing costs. Your servicer sets the amount and the minimum lump sum.

Can I recast more than once?

Some servicers permit it, others limit it. It is set by policy rather than by regulation, so ask.

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